Clinical Applications
One of the primary functions of the dentist is to prevent, intercept, and treat diseases or disorders affecting the dentition. It is also essential that the clinician be aware of the location and size of the pulp cavities during operative procedures to prevent unnecessary encroachment on the pulp. It is also incumbent on the clinician to know the location of the mandibular canal and nerve.
Endodontic procedures also require a thorough knowledge of the pulp cavity. Perforation during access preparation, failure to locate all the canals, or perforation of the root surface may result in the ultimate loss of the tooth. Therefore the clinician performing endodontics must know the size and location of the pulp chamber and the expected number of roots and canals.
Radiographic detection of all accessory roots or canals may not be possible, although some evidence is present based on the shape of the crown that additional canals are present. Even so, the clinician must recognize some of the internal signs of additional canals during the endodontic procedure. With a thorough knowledge of the pulp cavities in the permanent dentition, prevention, interception, and treatment of dentition-related disease processes will be accomplished with a greater degree of success.
FIGURE 13-7 A, Molar and bicuspid pulp cavities. Note the prominence of the pulp horns and the complexities of the pulp chambers and root canal systems. B, Microcomputed tomographic scans of dental anatomy (36 pm resolution). 1, Clinical view of tooth #9 shows two accessory canals and an apical bifurcation. 2, Mesiodistal view of the tooth shown in 1. 3, Working length radiograph with files placed in both apical canal aspects. C, Microcomputed tomographic scans of more complicated dental anatomy (36 pm resolution). 1, Clinical view of tooth #3 shows a fine mesiobuccal and distobuccal canal system with additional anatomy in all three roots. 2, Mesiodistal view of the tooth shown in 1.
Pulp Cavities of the Maxillary Teeth
MAXILLARY CENTRAL INCISOR
Labiolingual Section
The pulp cavity follows the general outline of the crown and root. The pulp chamber is very narrow in the incisal region. If a great amount of secondary or irritation-induced dentin has been produced, this portion of the pulp chamber may be partially or completely obliterated (Figure 13-8, A, 3). In the cervical region of the tooth, the pulp chamber increases to its largest labiolingual dimension.
Below the cervical area, the root canal tapers, gradually ending in a constriction at the apex of the tooth (apical constriction). The apical foramen is usually located near the very tip of the root but may be located slightly to the labial (Figure 13-8, A, 3, 4, and 5) or lingual aspect of the root (Figure 13-8, A, 1 and 6 ). Because of this generalized phenomenon it has been suggested that the root canal filling should appear on radiographs to extend no closer than 1 mm from the radiographic apex of the tooth. However, with the use of an electronic apical locator the clinician can have more confidence in more closely reaching the apex without overfilling.
Mesiodistal Section
The pulp chamber is wider in the mesiodistal dimension than in the labiolingual dimension. The pulp cavity conforms to the general shape of the outer surface of the tooth. If prominent mamelons (see Figure 1-10, B) are or have been present, it is not unusual to find definite prolongations or pulp horns in the incisal region of the tooth (Figure 13-8, B, 5 and 6). The pulp cavity then tapers rather evenly along its entire length until reaching the apical constriction. The position of the apical foramen is usually slightly off center from the tip of the root, but some foramina deviate drastically from the apex of the root (Figure 13-8, B, 6).
Cervical and Midroot Cross Sections
The pulp cavity is widest at about the cervical level, and the pulp chamber is generally centered within the dentin of the root (Figure 13-8, C, 1 through 5 ). In young individuals the pulp chamber is roughly triangular in outline, with the base of the triangle at the labial aspect of the root (Figure 13-8, C, 5 ). As the amount of secondary or reactive dentin increases, the pulp chamber becomes more round or crescent-shaped (Figure 13-8, C, 3, 4, and 6). The outline form of the root at the cervical level is typically triangular with rounded corners (Figure 13-8, C, 5 and 6), but some are more rectangular or angular with rounded corners (Figure 13-8, C, 1 through 4 ). The root and pulp canal tend to be rounder at the midroot level (Figure 13-8, D, 1 through 6 ) than at the cervical level. The anatomy at the midroot level is essentially the same as that found at the cervical level, just smaller in all dimensions.
Figure 13-8 Maxillary central incisor. Sections of natural specimens. A, 1 through 6, Labiolingual sections. This aspect does not appear in radiographs. B, 1 through 6, Mesiodistal sections. C, 1 through 6, Cervical cross sections of root. D, 1 through 6, Midroot cross sections.
MAXILLARY LATERAL INCISOR
Labiolingual Section
The anatomy of the lateral incisor is similar to that of the central incisor. The pulp cavity of the lateral incisor generally follows the outline form of the crown and the root. The pulp horns are usually prominent. The pulp chamber is narrow in the incisal region and may become very wide at the cervical level of the tooth (Figure 13-9, A, 1, 2, 3, and 5). Those teeth lacking this cervical enlargement of the pulp chamber possess a root canal that tapers slightly to the apical constriction (Figure 13-9, A, 4 and 6). Many of the apical foramina appear to be located at the tip of the root in the labiolingual aspect (Figure 13-9, A, 1, 4, and 6), whereas some exit on the labial (Figure 13-9, A, 2, and 3) or lingual aspect of the root tip (Figure 13-9, A, 5).
Mesiodistal Section
The pulp cavity closely follows the external outline of the tooth. The pulpal projections or pulp horns appear to be blunted when viewed from the labial aspect of the tooth. The pulp chamber and root canal gradually taper toward the apex, which often demonstrates a significant curve toward the distal in the apical region (Figure 13-9, B, 1 through 4, and 6).
Cervical and Midroot Cross Sections
The cervical cross section shows the pulp chamber to be centered within the root. The root form of this tooth shows a large variation in shape.The outline form of this tooth may be triangular, oval, or round (Figure 13-9, C, 1 through 6 ). The pulp chamber generally follows the outline form of the root, but secondary dentin may narrow the canal significantly (Figure 13-9, D, 4 and 6).
MAXILLARY CANINE
Labiolingual Section
The maxillary canine has the largest labiolingual root dimension of any tooth in the mouth. Because the pulp cavity corresponds closely to the outline of the tooth, the size of the pulp chamber of this tooth may also be the largest in the mouth.
The incisal aspect of the canine corresponds to the shape of the crown. If a prominent cusp is present, a long narrow projection from the pulp chamber (the pulp horn) will be present. The pulp chamber and incisal third or half of the root canal may be very wide, showing a very abrupt constriction of the root canal in the apical region, which then gently tapers toward the apex (Figure 13-10, A, 4, 5, 6, and 8; D, 16, 17, and 18). In other instances, a root canal may taper evenly from the pulp chamber to the apex of the root (Figure 13-10, A, 9; D, 10, 11, 13, and 14).
Figure 13-9 Maxillary lateral incisor. Sections of natural specimens. A, 1 through 6, Labiolingual sections. This aspect does not appear in radiographs. B, 1 through 6, Mesiodistal sections. C, 1 through 6, Cervical cross sections of root. D, 1 through 6, Midroot cross sections.
Some canines have severe curves in the apical aspect of the root (Figure 13-10, A, 3 and 7). The apical foramen may appear to exit at the tip of the root (Figure 13-10, A, 2 and 5 through 8; D, 11, 17, and 18 ) or labially to the apex of the root (Figure 13-10, A, 1, 3, and 4; D, 12 through 16).
Mesiodistal Section
The pulp cavity is much narrower in the mesiodistal aspect. The dimension and degree of taper of the pulp canal of the maxillary canine are very similar to those of the central and lateral incisors; however, the cuspid has a much longer root. The pulp cavity gently tapers from the incisal aspect to the apical foramen. A mesial or distal curve of the apical root may be present (Figure 13-10, B, 1, 4, 6, and 8; E, 14, 17, and 18). The apical foramen may appear to exit at the tip of the root (Figure 13-10, B, 1, 3 through 5, 7, and 9; E, 10, 11, 13, 14, 17, and 18) or slightly to the mesial or distal aspect of the root (Figure 13-10, B, 2, 6, and 8; E, 12, 15, and 16 ).
Cervical Cross Section
In cervical cross section, the shape of the root and pulp cavity is oval (Figure 13-10, C, 6, 7, and 9), triangular (Figure 13-10, C, 8), or elliptical (Figure 13-10, C, 1 through 5). The pulp chamber and canal are often centered within the crown and root (Figure 13-10, C, 1, 3, 4, and 9).
MAXILLARY FIRST PREMOLAR
Buccolingual Section
The maxillary first premolar may have two well-developed roots (Figure 13-11, A, 1, 2, and 9; D, 10 and 14), two root projections that are not fully separated (Figure 13-11, A, 3, 5, 7, and 8; D, 11, 12, 13, 15, 16, and 17), or one broad root (Figure 13-11, A, 4 and 6; D, 18). The majority of maxillary first premolars have two root canals (Figure 13-11, A and D). A small percentage of maxillary first premolar teeth may have three roots that may be almost undetectable radiographically.
The pulp horn usually extends further incisally under the buccal cusp, because this cusp is usually better developed than the lingual cusp. The pulp horns may be blunted (Figure 13-11, A, 1, 5, and 6; D, 11) in teeth possessing cusps that demonstrate a fair amount of attrition. The pulp chamber floor is below the cervical level of all the variations found in the maxillary first premolar. The pulp chamber of teeth having the least root separation usually shows the largest incisal-apical dimension (Figure 13-11, A, 4; D, 18). Those teeth possessing a partial root separation may also have this large dimension (Figure 13-11, A, 8; D, 10). Teeth having two separate canals usually demonstrate a rather small pulp chamber in the incisal-apical direction (Figure 13-11, A, 1, 2, and 9; D, 11 and 14). The shape of the pulp chamber (excluding the pulp horns) tends to be square (Figure 13-11, A, 1 and 8; D, 10, 12, 13, 14, and 18) or rectangular (Figure 13-11, A, 2 through 7; D, 11, 15, 16, and 17 ).
Figure 13-10 Maxillary canine. A, Labiolingual section, exposing the mesial or distal aspect of the pulp cavity. This aspect does not appear on dental radiographs. B, Mesiodistal section, exposing the labial or lingual aspect of the pulp cavity. C, Cervical cross section at the cementoenamel junction exposing the pulp chamber. These are the openings to root canals that will be seen in the floor of the pulp chamber. D, Labiolingual section, exposing the mesial or distal aspect of the pulp cavity. E, Mesiodistal section, exposing the labial or lingual aspect of the pulp cavity.
The root canal often appears to exit at the tip of the root (Figure 13-11, A, 1, 4, 6, 7, and 8; B, 12, 13, and 15 through 18), slightly to the labial or lingual (Figure 13-11, A, 2), or a combination of the two locations (Figure 13-11, A, 3, 5, and 9; B, 10, 11, and 14).
Mesiodistal Section
The pulp horns appear blunted from the mesial or distal aspect, and the pulp chamber cannot be differentiated from the root canal. The pulp cavity tapers slightly from the occlusal aspect to the apical foramen. If two canals are present, the radiopacity will increase in the apical half of the tooth because of an increased amount of dentin and bone and a decrease in the volume of the pulp cavity.
The apical foramen appears to exit at the tip of the root most of the time (Figure 13-11, B, 1, 2, 3, and 6 through 9; E, 10 and 12 through 18), but some appear to exit on the mesial or distal aspects of the root (Figure 13-11, B, 4 and 5; E, 11).
